Laminated non-woven fabric



J 27, 1967 R. c. SOKOLOWSKI LAMINATED NON-WOVEN FABRIC 2 Sheets-Sheet zFiled June 21, 1965 United States Patent 3,327,708 LAMINATED NON-WOVENFABRIQ Robert C. Sokolowski, Menasha, Wis., assignor to Kim= berly-ClarkCorporation, Neenah, Wis., a corporation of Delaware Filed June 21,1965, Ser. No. 465,609 7 Claims. (Cl. 128-155) This is acontinuation-in-part of copending patent application Ser. No. 286,294,filed June 7, 1963 now abandoned.

This invention relates to improvements in lightweight, laminated webs ofa non-woven type particularly adapted for use as cover material forabsorbent sanitary products such as sanitary napkins, absorbent pads,diapers and the like.

A primary object of the invention is to provide an improved light-weightfabric of high flexibility and strength, characterized by a very softhand and feel, having low resistance to fluid passage therethrough whilepresenting substantial resistance to scufling, wet rub, and deformingtensions in normal use.

Another object is to provide an improved laminated web which combinesthe advantages of a smooth bodycontacting surface of substantiallyaligned very low denier synthetic fibers with the permeability of anunderlying creped wadding element associated therewith.

A further object is to provide a method for the economical, high-speedmanufacture of a web of the character indicated.

Other objects and advantages will become apparent to persons skilled inthe art upon examination of the drawings and specification, the scope ofthe invention being defined in the appended claims.

In the drawings, in which like parts are identified by the samereference numerals:

FIG. 1 illustrates in elevation one form of production apparatussuitable for fabrication of the improved product herein taught.

FIG. 2 shows fragmentarily, in plan, the surface of an intaglio printingroll employed in applying adhesive to a web of creped wadding whichbecomes an integral part of the laminated web.

FIG. 2A is similar to FIG. 2 but shows another variation of an intagliopattern for a printing roll.

FIG. 3 is a greatly enlarged sectional view of a fabric productincorporating the invention, illustrating the assembled relationship ofthe laminated components.

FIG. 4 is a micro-photograph showing a plan view of a product fabricatedin accordance with the principles herein taught.

Since the introduction of synthetic monofilaments and staple fibersformed therefrom, many attempts have been made economically to employvery thin and light-weight layers of either monofilaments or fibers ofvery low denier in a manner to render a resulting product suitable foruse as sanitary napkin wrappers or the like. It is known that whenstaple length fibers such as cotton, and synthetic fibers in the denierrange of 0.5 to 3 obtained from such materials as viscose or acetaterayon, nylon, polyesters, acrylonitriles, and the like, are formed insubstantial alignment and contiguously disposed, as from the output of adrawframe, they provide an assembly of considerably increased tensilestrength, when bonded, over ordinary carded webs.

Means for drawing cotton fibers to their maximum length by lengthwisetensioning and alignment into a striated web of uniform density for usein structural materials are described in United States Patent 2,407,548of Sept. 10, 1946. A method and apparatus substantially as describedtherein, which includes carding, silver forming, lapping, and repeateddrafting operations, is utilized in this invention to form a suitablestarting web from synthetic fibers for subsequent lamination as definedherein. The drafting process is merely preliminary to the inventionherein disclosed. The invention is directed primarily to the furtherprocessing of a highly drafted web, as obtained from the aboveoperations, in a manner to make it especially useful for employment as asanitary napkin wrapper or the like.

The use of highly drafted fibers as light-Weight webs for sanitarynapkin and bandage wrappers has heretofore been deemed impracticalbecause of the difiiculties involved in suitably binding the fiberstogether while retaining permeability, soft hand and drape. This isparticularly true when the fibers are of a very low denier, for example,of a denier range of 0.5 to 3. Non-bonded webs formed solely of highlydrafted fibers within the above denier range are extremely delicate, andit is difii-cult to maintain such webs in tensioned unitary assemblywhile applying a suitable adhesive. Also, because of their light-weightnature, a substantial amount of adhesive is needed to strengthen thewebs sufliciently to serve a useful purpose. The amount of adhesiverequired to insure acceptable form-sustaining properties not onlyresults in web stiflening and resultant loss of desirable hand and feel,but also substantially increases resistance to fluid penetrationtherethrough.

Attempts were made to print the flimsy webs resulting from the draftingoperation directly with thermoplastic adhesives in order to avoid thestiffness which results from the use of the easier applied thermosettingmaterials. These attempts failed principally because the tackiness ofthe adhesive on the printing roll tended to pull out fibers, destroytheir substantial alignment and disrupt the desired uniform formation.Temporarily bonding the drawn web with adhesives which subsequentlycould be washed out aided the situation somewhat, but the resulting webhad little cross-direction strength and required the use of inordinateamounts of adhesive which penetrated to both sides of the web and leftan undesirable uneven finish and poor permeability, in addition todetracting from softness and drape.

The present invention overcomes the above disadvantages by employing anovel method of incorporating the adhesive into the finished web. Themethod utilizes a carrier web on which thermoplastic adhesive in thedesired open pattern is first applied. The highly drafted fiber web isthen positioned on the adhesive without disturbing the aligned fiberarrangement. The carrier we-b subsequently becomes an integral part ofthe finished fabric, and provides desirable cross-direction strength andfluid permeability without detracting from flexibility and softness.

The invention, therefore, is directed to an improved non-woven multi-plyweb assembly, one ply of which consists of substantially alignedsynthetic monofilaments or highly drafted and aligned staple fibers ofvery low denier and of very light weight, while another ply comprises alight-weight web of cellulose wadding. The web assembly is such that themonofilaments or long staple fibers are retained in form-sustainingalignment to insure the maintenance of high tensile strength withoutdestroying surface smoothness or softness. This is accomplished bypermanently embedding the fibers, while held under tension, into a soft,flexible, substantially cured, thermoplastic adhesive which has beensuitably applied to the underlying creped wadding web.

vantages include a silk-like appearance and soft feel, high tensilestrength, good flexibility, and substantial non-adherence to the bodysurface in use.

The improved product includes a light-weight creped wadding base layer,having applied to one side thereof a soft and flexible adhesive confinedin a patterned configuration to a minor portion of the base layer.Selected portions of substantially aligned synthetic fibers, applied inthe form of a tensioned thin layer, are bonded to the base layer byembedment in said adhesive. It is very important that the adhesivebonding of the surface fiber layer to the base layer of creped waddingbe effected in a manner to retain the synthetic fibers in tensionedalignment while keeping the top surface of the fiber layer substantiallyfree of adhesive. The process as herein defined permits lamination andbonding to be carried out at high speeds without disturbing the delicatefiber arrangement.

As shown in FIG. 1, a creped wadding sheet 11, which has been stretchedand ironed to facial tissue softness by known means, is drawn from asupply roll into a nip formed between a printing roll 12 and preferablya backup roll 14 maintained in very light pressure engagement with sheet11. Printing roll 12 is provided with an intaglio printing pattern, suchas the diamond pattern shown in FIG. 2. Grooves 16 of roll 12 arecontinuously supplied with a low viscosity thermoplastic adhesive 18from dip pan 19, part of the adhesive thus applied being removed bydoctor blade 20 prior to transfer of a metered amount of adhesive to theWadding in the patterned configuration provided by grooves 16. Othersuitable adhesive patterns may be employed, it being important, however,that the pattern of applied adhesive be substantially open, and that thetotal area occupied by the adhesive comprise not more than 25% of thetotal area of the final product, and preferably only about or less ofthat area. For maximum transverse strength, the pattern chosen may beinterconnected, as for example the diamond pattern of FIG. 2, in whichthe lines of adhesive cross each other. Alternatively, a grid-likepattern, wherein the lines extend transversely of the web in spacedparallel arrangement and the adhesive in each line is substantiallycontinuous, may be used. However, for improved flexibility, betterdrape, and softer hand, the adhesive may be applied in the form ofspaced, discontinuous areas or broken lines, in which the discontinuousportions provide a staggered pattern of fiber attachment. When a patternof spaced discontinuous lines of adhesive is provided, those lines arepreferably parallel and disposed substantially perpendicularly to thedirection of the aligned fibers. A fragmentary showing of a roll surfacehaving such a pattern is shown in FIG. 2A wherein the grooves 16aprovide a brick-like pattern of adhesive. Other angular dispositions ofadhesive patterns with respect to the direction of fiber lay are alsouseful. Further variations in shape, size and arrangement of theadhesive pattern may be employed. An important factor, however, is that,no matter what pattern is chosen for the desired open configuration, thespacing between the areas of adhesive measured between adjoiningadhesive areas in the longitudinal direction of the web preferablyshould be less than the average fiber length in order that thecross-directional integrity of the web is maintained.

The applied adhesive penetrates part way into the wadding with asubstantial portion remaining on the surface. Some lateral migration ofadhesive also occurs, but itis important that the amount applied becontrolled so that the total area of the adhesive pattern after suchmigration does not exceed, as above mentioned more than about 25% andpreferably not more than about 15% of the total area of the wadding, inorder to preserve the openness as well as the flexibility of the finalproduct. The Wadding thus printed is drawn from the output nip of theprinting and backing rolls, around roll 24 positioned closely adjacent adrawframe or the like 26. A web 28a of substantially aligned syntheticfibers of a denier in the range of 0.5 to 3, which has been formed anddrafted as previously described by passing multiple slivers 28 of staplelength synthetic fibers through drawframe 26, is applied, while undercontinuous tension, onto that side of the base sheet 11 to which theadhesive pattern has previously been printed. A sufficient number offibers are provided in the multiple slivers 28 to result in theformation of a substantially aligned highly drafted web 28a, at theoutput of drawframe 26, having a weight between about 3 and 20 grams persquare yard.

The two-ply laminated material thus formed is drawn from guide roll 24over guide roll 30 and around heated drum 32 where curing of theadhesive is substantially completed to a non-tacky condition while web28a is in firm contact therewith. As shown in the drawings, the curingoperation is carried out with the layer of fibers forming the upper plyof the laminate in contact with the heated surface of drum 32.Alternatively, the creped wadding side may be positioned against theheated surface. To provide effective heat curing of the adhesive, travelthereof around a substantial portion of drum 32 is desirable. For thispurpose, the calender roll 34, which presses the fiber layer intoadhesive at pressure nip 35 while the curing is being completed, ispositioned downstream of the top of the drum, somewhat as shown, toutilize a substantial arc of the peripheral drum surface for the earlierstages of curing. Auxiliary heating means, including additional heatedrolls, hot air streams, or radiant heaters, may be positioned eitherbefore or after the calendering step to speed up the curing and insurethat such curing is complete.

It will be noted that creped wadding base sheet is continuouslysubjectedto tension during its travel from the supply roll 10 tofinished roll 13, the tension being provided by driven rolls 12, 34, and40. The web output 28a from drawframe 26 is maintained under a likedegree of tension as the laminate is pulled around heated drum 32, sothat substantially all of the fibers remain in their aligned conditionwhile curing and pressure bonding take place. The fully cured product isdrawn around guide rolls 36 and 38 by a driven roll 40 for windup on aspindle 42 carried by a bracket 44 pivoted at 46.

FIG. 4 is a micro-photograph in plan view of the finished laminate,illustrating how substantially all of the fibers 48 are held in parallelalignment by lines of adhesive 15. The relatively small amount of fiberswhose ends elude complete embedment in the adhesive are free to assume arelaxed state and form a somewhat fuzzy surface, as shown in themicro-photograph, which adds to the desirable soft cosmetic feel in thefinished product.

FIG. 3 illustrates, in greatly enlarged and somewhat exaggerated form,the arrangement of the individual drawn fibers with respect to theadhesive and the creped wadding base sheet. The section is takensubstantially along a continuous area of adhesive, of which line 33 ofFIG. 4 is representative, to illustrate more clearly the preferredstructure. Note that, as shown in FIG. 3, the line of adhesive 15penetrates into the creped wadding 11 to a considerable extent toprovide firm bonding therewith while the fi'bers'48 are only partiallyembedded into the adhesive with essentially no adhesive extending beyondthe upper surface of the fibers. The upper surface of the resultingproduct thus is desirably smooth and free of adhesive, making itparticularly adapted for use as wrappers for sanitary napkins, coversfor disposable diapers, surfacing material for absorbent pads andbandages, and for many similar uses.

While various adhesives may be employed, advantages reside in the use ofplastisols, which as is well known, are colloidal dispersions ofsynthetic resins in a suitable organic ester plasticizer. While manyadhesives of this nature are known, those found particularly useful forincorporation in the product of this invention include vinyl chloridepolymers, and copolymers of vinyl chloride with other vinyl resins,plasticized by organic phthalates, sebacates, adipates, or phosphates.These provide a fast curing plastisol adhesive characterized byrelatively low viscosity, low migration tendencies, and minimumvolatility. Such adhesives remain soft and flexible after curing, andinsure that the resultant laminate product retains the desired softnessand proper hand and feel.

The base sheet of creped cellulose wadding preferably has a basis weightbefore creping of between about 4 and 12 pounds per 2880 square footream. The sheet may have a crepe ratio of between about 1.1 and 2.5 whencreped off the drier on the paper machine, and preferably contains Wetstrength resins, although such latter treatment is not essential. Anyconventional method of imparting wet strength may be employed such asthose described in TAPPI Monograph No. 13, Wet Strength in Paper andPaperboard. The methods usually employed comprise incorporating amelamine formaldehyde, urea formaldehyde, polyalkylene polyamine, orsimilar resin in the pulp furnish. Conventional wetting agents may alsobe employed to prevent loss of water absorbency which the wet-strengthtreatment may engender.

It is preferred also that the creped wadding sheet be formed in such amanner as to produce an open or perforated formation in order to enhancerapid fluid pene tration in the final laminated product. A patterned orspecially woven screen in the forming area of the paper machine may beutilized for such purpose, or the formed sheet may be subsequentlyperforated by a suitable needling operation. While a sheet with openformation is preferred, a regularly formed wadding sheet may also beused.

It is also preferred that the creped web be stretched and ironed aftercreping to reduce the crepe ratio to about 1.1 to 1.5 and to produce asoft sheet such as is customarily used in the manufacture of facialtissues. Generally, the base sheet should possess good bulk, softness,absorbency, permeability, and strength.

The synthetic monofilaments or staple length fibers employed shouldpreferably be of a denier in the range of 0.5 to 3. When fibers areused, as in the preferred embodiment, they should be of staple length,or in the range of /1 to about 3 inches or longer, with the majority offibers being at least one inch in length. The drafted web should be aslight weight as possible commensurate with handleability on the drawingframe. Suitable webs in the weight range of 3 to 20 grams per squareyard have been successfully drafted and laminated at speeds of from 20feet per minute to well over 500 feet per minute.

As is known to those skilled in the art, highly drafted webs of staplelength fibers have approximately 80% to 95% of their fibers orientedsubstantially in the machine direction. This high degree of alignment isimportant to the invention and should be distinguished from conventionalcarded webs wherein only about 50% to 70% of the fibers aresubstantially longitudinally aligned. When ever the term highly draftedwebs is used in the specificalion and claims, it means webs in whichabout 80% to 95% of the fibers are aligned substantially in the machinedirection.

Having now described the invention in general terms, the followingspecific example is given to provide a more detailed account of theprocess and product involved.

A creped wadding sheet having a basis weight before creping of 6.5pounds per 2880 square feet and a crepe ratio of 2.2, was stretched andironed to a finished crepe ratio of about 1.2. This sheet was printed ina diamond pattern with a plastisol adhesive, in the manner abovedescribed, to cover approximately 21% of the surface area. The adhesivewas applied in the amount of about 6.1 grams per square yard andconsisted of 100 parts of polyvinyl chloride resin dispersed in 60 partsby weight of dioctyl phthalate and thinned with mineral spirits. A webof highly drafted fibers and having a weight of 7.1 grams per squareyard, comprised substantially of 2.5 inch long fibers of 1.5 denierviscose rayon, in which about of the fibers were parallelly aligned inthe machine direction, was fed into contact with the adhesive printed onthe creped wadding web. The combined web was drawn under tension over aheated drum operated at a temperature of about 325 P. where the adhesivewas substantially cured while the fibers were pressed therein bycalendering as shown.

The finished web was tested for tensile strength on an Instron testerand found to have a breaking strength of 2.93 lbs/inch in the machinedirection and 0.21 lb./inch in the cross direction.

A similar laminate was prepared using as the top element, in place ofthe highly drafted web, a conventional carded web in which approximately60% of the fibers were longitudinally aligned. The carded web weighed7.25 grams per square yard. This laminate tested out at a breakingstrength of 1.04 lbs/inch in the machine direction and 0.28 lb./inch inthe cross direction.

While only one specific embodiment of the inventive concept has been setforth herein, it is understood that the invention is not to be construedas limited thereby, and that any suitable changes, modifications, andvariations may be made without departing from the spirit and scope ofthe invention as defined in the appended claims.

What is claimed is:

1. A laminated fabric comprising a base web of lightweight crepedcellulose wadding, a thin overlying web of synthetic fibers in which 80to percent of the fibers are parallelly aligned in fully extended andstraight condition, and an intermediate binding layer comprising anelastomeric adhesive disposed in the form of a regularly spaced patternof an open configuration between said webs, said webs being bondedtogether by said adhesive only in the areas define-d by said adhesivepattern, and the fibers of said overlying web being bonded and held inalignment by imbedment in said adhesive.

2. A laminated fabric as set forth in claim 1, in which said adhesive atleast partially penetrates said wad-ding and the top surface of saidoverlying web is substantially free of adhesive.

3. A laminated fabric as set forth in claim 1, in which the cellulosewadding has an open formation.

4. A laminated fabric as set forth in claim 1, in which the celluulosewadding contains wet strength resin.

5. A laminated fabric as set forth in claim 1, in which the fiber web isin the weight range of about 3 to 20 grams per square yard.

6. A laminated fabric as set forth in claim 1, in which the adhesive isa plastisol adhesive.

7. A laminated fabric as set forth in claim 1, in which the adhesvepattern covers an area comprising about 15 to 25 percent of the totalarea of said webs.

References Cited UNITED STATES PATENTS 2,295,439 9/1942 Voigtman 16l146X 2,625,161 1/1953 Johnson 156291 X 2,705,497 4/1955 Johnson et a1.16l148 3,047,444 7/1962 Harwood 156 29l X 3,047,445 7/1962 Gresham16l148 X FOREIGN PATENTS 419,852 4/ 1944 Canada.

MORRIS SUSSMAN, Primary Examiner. ALEXANDER WYMAN, Examiner.

1. A LAMINATED FABRIC COMPRISING A BASE WEB OF LIGHTWEIGHT CREPEDCELLULOSE WADDING, A THIN OVERLYING WEB OF SYNTHETIC FIBERS IN WHICH 80TO 95 PERCENT OF THE FIBERS ARE PARALLELLY ALIGNED IN FULLY EXTENDED ANDSTRAIGHT CONDITION, AND AN INTERMEDIATE BINDING LAYER COMPRISING ANELASTOMERIC ADHESIVE DISPOSED IN THE FORM OF A REGULARLY SPACED PATTERNOF AN OPEN CONFIGURATION BETWEEN SAID WEBS, SAID WEBS BEING BONDEDTOGETHER BY SAID ADHESIVE ONLY IN THE AREAS DEFINED BY SAID ADHESIVEPATTERN, AND THE FIBERS OF SAID OVERLYING WEB BEING BONDED AND HELD INALIGNMENT BY IMBEDMENT IN SAID ADHESIVE.